{"schema_version":"1.9.0","id":"CVE-2026-63949","published":"2026-07-19T14:55:42.679Z","modified":"2026-08-31T18:26:08.447850954Z","related":["SUSE-SU-2026:23066-1","SUSE-SU-2026:23068-1","SUSE-SU-2026:23193-1","SUSE-SU-2026:23194-1","SUSE-SU-2026:23221-1","SUSE-SU-2026:23231-1","SUSE-SU-2026:23237-1","SUSE-SU-2026:23241-1","SUSE-SU-2026:23244-1","SUSE-SU-2026:3790-1","SUSE-SU-2026:3810-1","openSUSE-SU-2026:21555-1"],"summary":"auxdisplay: line-display: fix OOB read on zero-length message_store()","details":"In the Linux kernel, the following vulnerability has been resolved:\n\nauxdisplay: line-display: fix OOB read on zero-length message_store()\n\nlinedisp_display() unconditionally reads msg[count - 1] before\nchecking whether count is zero, so a write of zero bytes to the\nmessage sysfs attribute hits msg[-1]:\n\n\twrite(fd, \"\", 0);\n\n\t-> message_store(..., buf, count=0)\n\t   -> linedisp_display(linedisp, buf, count=0)\n\t      -> msg[count - 1] == '\\n'  ; OOB read\n\nThe kernfs write buffer for that store is a 1-byte allocation\n(kernfs_fop_write_iter() does kmalloc(len + 1) with len == 0),\nso msg[-1] is a 1-byte read before the slab object. On a\nKASAN-enabled kernel this trips an out-of-bounds report and\npanics; on stock kernels it silently reads adjacent slab data\nand, if that byte happens to be '\\n', the following count--\nwraps ssize_t 0 to -1 and is then passed to kmemdup_nul().\n\nlinedisp_display() is reached from the message_store() sysfs\ncallback (drivers/auxdisplay/line-display.c message attribute,\nmode 0644) and from the in-tree initial-message setup with\ncount == -1, so the OOB path is only userspace-triggerable via\nzero-byte writes; vfs_write() does not short-circuit on\ncount == 0 and kernfs_fop_write_iter() dispatches the store\ncallback regardless.\n\nGuard the trailing-newline trim with a count check. The\nexisting if (!count) block then takes the clear-display path\nunchanged.\n\nAffects every auxdisplay driver that registers via\nlinedisp_register() / linedisp_attach(): ht16k33, max6959,\nimg-ascii-lcd, seg-led-gpio.","affected":[{"ranges":[{"type":"GIT","repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","events":[{"introduced":"7e76aece6f036cb7ada4858d6aa73825bfe22983"},{"fixed":"ca5b0781946d5083ceafa752141f47f085853620"},{"fixed":"8776032fe989a9b5fc77f2de5e03e4adb44c630e"},{"fixed":"3859960daeb9b7b39b9847b5b0113bc6081eb735"},{"fixed":"197476b126010bac1b3199833c6966cd6f54c2a9"},{"fixed":"6ad4f75ef9f3372fce8cad494e789ac6a5507bef"},{"fixed":"a7511dcd9dd4bc55d123f9b800c8a4ed2662e5c6"}]}],"database_specific":{"source":"https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-63949.json"}},{"package":{"name":"Kernel","ecosystem":"Linux"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"5.16.0"},{"fixed":"6.1.176"}]},{"type":"ECOSYSTEM","events":[{"introduced":"6.2.0"},{"fixed":"6.6.143"}]},{"type":"ECOSYSTEM","events":[{"introduced":"6.7.0"},{"fixed":"6.12.93"}]},{"type":"ECOSYSTEM","events":[{"introduced":"6.13.0"},{"fixed":"6.18.35"}]},{"type":"ECOSYSTEM","events":[{"introduced":"6.19.0"},{"fixed":"7.0.12"}]}],"database_specific":{"source":"https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-63949.json"}}],"references":[{"type":"WEB","url":"https://git.kernel.org/stable/c/197476b126010bac1b3199833c6966cd6f54c2a9"},{"type":"WEB","url":"https://git.kernel.org/stable/c/3859960daeb9b7b39b9847b5b0113bc6081eb735"},{"type":"WEB","url":"https://git.kernel.org/stable/c/6ad4f75ef9f3372fce8cad494e789ac6a5507bef"},{"type":"WEB","url":"https://git.kernel.org/stable/c/8776032fe989a9b5fc77f2de5e03e4adb44c630e"},{"type":"WEB","url":"https://git.kernel.org/stable/c/a7511dcd9dd4bc55d123f9b800c8a4ed2662e5c6"},{"type":"WEB","url":"https://git.kernel.org/stable/c/ca5b0781946d5083ceafa752141f47f085853620"},{"type":"ADVISORY","url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/63xxx/CVE-2026-63949.json"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-63949"},{"type":"PACKAGE","url":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git"}],"database_specific":{"cna_assigner":"Linux","osv_generated_from":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/63xxx/CVE-2026-63949.json"}}